This invention relates generally to wireless communication systems, and more particularly to a technique for high speed re-allocation of coded radio channel resources that are shared among a number of users.
Demand for wireless communications equipment and services continues to grow at an unprecedented rate throughout the world. Increasingly, such systems are commonly relied upon to provide voice and data communications to a growing sector of the public. While these systems originally depended upon analog signaling technology, there is essentially unanimous agreement that future systems will be based on various types of digital signal coding schemes.
The typical wireless communication system is a point to multi-point type system in which a central base station communicates with a number of remote units located within a local geographic area of coverage known as a cell. This system provides for duplex communication such that signals may be sent in both a forward direction (from the base station to the remote unit) as well as in a reverse direction (from the mobile remote unit back to the base station). In order to support communication between the remote unit and networks such as the Public Switched Telephone Network (PSTN), or data networks such as the Internet, the wireless system must also provide for various other logical components and functional entities.
Consider the Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA) digital systems presently in widespread use. Each of these systems provides for certain logical types of the radio channels that make up the forward link and reverse link. In particular, the forward link channels often include a pilot channel, paging channels, and multiple forward traffic channels. The traffic channels are used to carry the payload data between the base station and the mobile unit. A pilot channel is also typically required to allow the remote unit to maintain synchronization with the base station. The paging channels provide a mechanism for the base station to inform the remote unit of control information, such as the assignment of particular forward traffic channels to particular connections and/or subscriber units.
Likewise, an access channel is provided in the reverse direction in addition to reverse traffic channels. The access channels allow the remote units to communicate control information with the base station, such as to send messages indicating the need to allocate or deallocate connections as required.
Unfortunately, users both compete for access to the available radio spectrum, while at the same time demanding data transmission rates that are as fast as possible. This situation is most acute in the forward link direction, where users of remote computing equipment are performing tasks such as accessing the World Wide Web. The forward link direction typically represents the direction of greatest data transfer, e.g., in connection with the downloading of web pages and files from remote servers.
It is critical therefore, for the channel allocation algorithms, and radio channel protocols to be as efficient as possible. As demand for access to the available radio spectrum changes almost instantly among a large group of users of such a wireless data network, maximum efficiency requires the ability to rapidly reassign channels. However, traditional wireless system architectures and protocols, such as those used in cellular telephone systems, were not designed with rapid channel changing in mind. They typically keep an end-to-end connection open for the duration of a session or call, and reassign channels only as a mobile unit moves from cell to cell.
Thus, these architectures use a protocol whereby a paging channel is used to send a message to a remote unit when a channel change is needed. The message is then received and acknowledged by the remote unit returning a channel acknowledgment to the central base station.
In an ideal wireless data environment, the channel assignments should be changeable many times during the duration of a given session, as instantaneous demand for access to the available radio bandwidth ebbs and flows, e.g., as individual users make requests to download web pages and files.